This invention relates to a governor for diesel engines, and more particularly to an electronic-mechanical governor adapted for use in a high-speed diesel engine for vehicles, which controls the engine speed by means of an electromagnetic actuator at low engine speeds and by means of a mechanical means utilizing a centrifugal force at high engine speeds.
The diesel engines for vehicles conventionally used mainly include mechanical governors which utilize the centrifugal force of flyweights and pneumatic governors which employ a diaphram. However, these conventional types of governors have the disadvantages that in the former type of governors the engine suffers hunting due to insufficient control of the engine speed at low speeds if the flyweights are designed small in size so as to comply with the spacewise limitation, while the latter type of governors are low in response to changes in the negative pressure in the intake pipe in the range of low engine speeds where the throttle valve of the venturi tube opens. On the other hand, in the diesel engines for vehicles, a governor which is capable of performing the control of the engine speed over a wide range of engine speeds in a stable manner has been desired in order to cope with the recent increased maximum speed of automobiles. In view of the above situations, in order to avoid the drawbacks in the both conventional governors and to exhibit the merits thereof, a governor has been proposed which comprises a combination of the two types of governors mentioned above in which the engine speed control is effected by means of the pneumatic governing mechanism utilizing the negative pressure in the intake pipe of the engine at low engine speeds, and by means of the mechanical governing mechanism utilizing the centrifugal force of the flyweights at high engine speeds. For instance, according to Japanese Utility Model Publication No. 22482/68, a governor for internal combustion engines of a fuel-injecting type which comprises a housing partitioned in two chambers by a partition wall; a pneumatic governing mechanism and a centrifugal or mechanical governing mechanism provided in respective ones of said chambers, the former mechanism having a diaphram connected to the fuel control rack of the fuel-injection pump and the latter mechanism having a shifter connected to a coupling means including two levers mounted in respective ones of said chambers and a push rod mounted in a fashion extending through said partition wall for transmitting the opening motion of the flyweights to the fuel control rack via said coupling means to move the fuel control rack in the fuel supply-decreasing direction, whereby the maximum engine speed is governed by the centrifugal or mechanical governor mechanism whereas the other ranges of engine speeds are governed by the pneumatic governor mechanism.
However, this type of governor has the following drawbacks and particularly it can difficultly cope with the recent exhaust-gas control;
(1) Since the amount of intake air charged into the engine is restrained by the venturi tube which is mounted in the intake pipe of the engine for control of the negative pressure in the intake pipe to actuate the pneumatic governor mechanism, the combustion efficiency of the engine is low, causing emission of smoke.
(2) If the exhaust gas recycle system (EGR) is employed in the engine for purification of the exhaust has, there occur irregular changes in the negative pressure in the interior of the venturi tube, which makes it difficult to ensure the regular operation of the pneumatic governing mechanism, thus impairing the controllability of the engine speed.
(3) In high places such as mountain districts where the atmospheric pressure varies largely and frequently, regular control of the engine speed cannot be performed by the pneumatic governing mechanism.
The present invention has been made in order to overcome the above-mentioned drawbacks in the conventional pneumatic-mechanical governor, and it is a primary object of the invention to provide an electronic-mechanical governor primarily adapted for use in a high-speed diesel engine for vehicles, which comprises a combination of an electronic governing mechanism and a mechanical governing mechanism and can perform stable and accurate control of the entire range of engine speeds in such a manner that the engine speed is controlled by the mechanical governing mechanism in the high-speed range and by the electronic governing mechanism in the low-speed range.
It is a further object of the invention to provide an electronic-mechanical governor which can exhibit an accurate and stable governing function over the entire range of engine speeds from the low-speed range to the high-speed range even if installed in an engine provided with exhaust gas purification measures such as the exhaust gas recycle system.